Color analyzer

ABSTRACT

A color analyzer for measuring a color synthesized by the additive mixture of primary colors, each having an arbitrary but constant relative spectral energy distribution. The color analyzer has a light receiving portion consisting of three or more photoelectric transducer elements equal in number to said primary colors and having independent spectral sensitivities, so as to generate electric quantities representing the received optical energy levels, and an electric calculating circuit for generating electric outputs representing the energy levels of said primary colors individually, independently and simultaneously. The color analyzer can also measure the luminance of the light source, and display CIE chromaticity.

United States Patent Kosaka et al.

COLOR ANALYZER Filed:

Mar. 1, 1972 Appl. No.: 230,725

Related US. Application Data Continuation-impart of Ser. No. 764,08i,Oct. i, 1968 abandoned.

Foreign Application Priority Data [451 Apr. 16, 1974 {56} ReferencesCited UNITED STATES PATENTS 2,7i6,7l7 8/1955Dresser.....r...r....m.......... 250/226 X OTHER PUBLICATIONS NHKLaboratories Note. Serial No. 137, December i970: A Colorimetric Meas.lnstrum. for TV Cameras. T. Saito, l5 pp.

Primary Examiner-Ronald L. Wibert Assistant Examiner-R J, WebsterAttorney, Agent. or FirmWaters, Roditi, Schwartz & Nissen {5 7] ABSTRACTA color analyzer for measuring a color synthesized by the additivemixture of primary colors. each having an 3 i32 japan arbitrary butconstant relative spectral energy distribu- 3 1968 Japan N8 tion. Thecolor analyzer has a light receiving portion 1968 Japan 54102 consistingof three or more photoelectric transducer r i968 Japan 43'64948 elementsequal in number to said primary colors and y 1968 Japan 43'69839 havingindependent spectral sensitivities, so as to gen- 1968 Japan 431/2947erate electric quantities representing the received opapan tical energylevels, and an electric calculating circuit for generating electricoutputs representing the energy ig l g gi ti 355 levels of said primarycolors individualiy, indepen- Int Cl 5 3/50 dently and simultaneouslyThe color analyzer can also "I measure the luminance of the lightsource, and display Field of Search 356/] 73i72s5jglg2gl05i CIEchmmaficity' 17 Claims, 22 Drawing Figures DG -fii 0!? OPT/07LDETECT/V/(i CWZCZ/ZAT/A/G l/VD/CAT/A/G SYSTEM ATENTEDAFR we m4 SHEET 010F 12 FIGZI FIG.2

MENTEDAPR as @974 am: as m 12 ATENTEB APR 1 6 I974 sum as $12 FIG. I5

CAL (0L4 77176 C 0960/ 7' m mgwn as IBM sum 11 ar 12 FIG/9 PATENTEUAPR15 I974 SKU 1201' 12 COLOR ANALYZER OTHER APPLICATIONS This applicationis a continuation-in-part of our earlier filed and copending applicationSer. No. 764,081, filed Oct. l, 1968, now abandoned.

FIELD OF INVENTIQN BACKGROUND Heretofore, several kinds of coloranalyzers have been proposed. According to one of these, firstly, spectral energies of a color to be analyzed are measured at various spectralwave lengths and then desired outputs are obtained through a complicatedcalculation by means of a computer to which the result of said measurement is applied. By using such apparatus, one may obtain accuratevalues for each of the colors, but such apparatus is too complicated instructure and too large in dimension to manufacture and use on acommercial basis. Further, this apparatus is not portable.

Furthermore, the conventional types of the known color analyzers areusually provided with three detec tors including respectively a colorfilter and a photoelectric element which has such spectralcharacteristics as to satisfy the Luther condition approximately,outputs of said detectors being directly read by means of indicatingmeans connected respectively with each of the detectors. Suchconventional analyzers, however, can be utilized for measurement only ofsuch colors as satisfy the Luther condition.

An analyzer not satisfying the Luther condition can measure quantitiesof primary colors in the color eonstituted by the additive mixture ofthe primary colors, if the correspondence between the spectralsensitivity of the detectors and the spectral distributioncharacteristics of the primary colors is effected. But it is verydifficult to attain such correspondence. Furthermore, in such analyzer,it is impossible to detect independently the quantity of each of theprimary colors, since the characteristic curves of the spectraldistributions of the primary colors partially overlap each other.

Recently, it has been required to detect independently the quantity ofthe primary colors of composite color by means of such detectors as donot satisfy the Luther condition, in the field, for instance, oftelevision broadcasting wherein the transmission system is adjusted bygenerating the chart image on the fluorescent screen of the monitortelevision so as to set thereon the reference white color, to measurethe quantity of the three primary colors included in said chart image.As will be described hereinafter, three primary colors of a coloremitted from the fluorescent screen of said color television partiallyoverlap with their characteristic curves of the spectral distribution.

For avoiding undesirable effects from said overlapping, the quantity ofthe three primary colors of such color television has been measured,hitherto, in such a manner that each of the primary colors is generatedindependently on the fluorescent screen of the monitor television tomeasure the quantity thereof.

However, the quantity of each of these three primary colors measuredwith respect to composite color emitled from the television differs fromthat measured independently with respect to each of the primary colors,since the former quantity is affected by the electric and/orelectromagnetic interference of the composite circuit.

SUMMARY OF INVENTION A primary object of the present invention is, thus,to provide a compact and portable color analyzer which can detectindependently the quantity of each of the primary colors of a colorproduced by the additive mixture thereof even if the detectors do notsatisfy the Luther condition and also when the characteristic curves ofspectral distribution of the primary colors partially overlap each otherand are not in correspondence with the spectral sensitivitycharacteristics of the detectors.

in the color analyzer of the present invention, if photoconductive cellssuch as CdS cells, or photovoltaic cells such as silicon cells (namelySBC) are used as photoelectric elements in the detectors, this is betterfor compactness and portability of the device, since they are small andrequire less electric power.

Therefore, another object of the present invention is to provide a coloranalyzer using photoconductive cells or photovoltaic cells in thedetectors as the photoelectric means.

It will be easily understood that, when the kinds of object to bemeasured are changed, the spectral distribution characteristics of itsprimary colors are changed in accordance therewith. Therefore, it isusually necessary to use for each one an expensive detecting devicecorresponding to each kind of object to be measured. A single detectingdevice has not heretofore been applicable to all of the kinds of objectsto be measured without a troublesome adjustment of said device each timethe object is changed.

Therefore, a further object of this invention is to provide a coloranalyzer wherein, when the kinds of object to be measured are changed,only a portion thereof is substituted for dealing with the change.

Furthermore, it is difficult for a device for generating referencecolors to be always available to adjust the detecting device. Forinstance, when a device as in the present invention is applied formeasurement of a colored light emitted from the fluorescent screen of acolor television set, it is necessary for some particular device to bealways available for generating the refer ence colors in thebroadcasting station, and it is also necessary to control it so that thereference colors can always be generated whenever needed. it is,however, difficult to maintain such conditions. The same applies to themanufacturing steps relating to said device. Moreover, in the lattercase, a particular device is required for each adjusting step.

A still further object of the invention is, therefore, to provide acolor analyzer wherein memory circuits generate respectively an outputidentical with the detector outputs generated for reference colors and,when the device must be adjusted, said memory circuits can be connectedin place of the detectors and, when the device is to be adjusted duringmanufacturing steps, said memory circuits can be substituted for thedetectors.

Furthermore, color analyzers prior to the present invention, whenapplied for the measurement of an image on a fluorescent screen of thecolor television set, were not able to detect effectively the lightenergy of the image, since light emitted from the restricted portion ofthe fluorescent screen is intermittent.

A still further object of the invention is, therefore, to provide acolor analyzer which detects effectively quantities of the primarycolors even if a light to be measured is emitted intermittently.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a graph illustrating anexample of the rela tive spectral distribution of three primary colorsof a colored light emitted from the fluorescent screen of a colortelevision set;

FIG. 2 is a block diagram illustrating the construction of the coloranalyzer in accordance with the present invention, wherein the partsother than the optical system are simplification of circuits asillustrated in FIGS. 6, 8, 10, I2, 15 and 20;

FIG. 3 is a graph showing an example of the spectral sensitivity of thedetectors in a color analyzer of the type shown in FIG. 2;

FIG. 4 is a chart illustrating spectral sensitivity;

FIG. 5 is a schematic diagram of another optical system including threephotoelectric elements;

FIG. 6 is a schematic diagram of a fundamental circuit of a coloranalyzer of the present invention, wherein photoconductive cells areused;

FIG. 7 is a block diagram illustrating an exchangeable calculatingcircuit and a memory device according to the present invention, whichcan be replaced for the corresponding portion in the circuits as shownin FIGS. 6, 8, l0, 12, 1S and 20;

FIG. 8 is an embodiment of the circuit shown in FIG.

FIG. 9 is a detailed diagram of the memory device in FIG. 7;

FIG. 10 is a schematic diagram of another fundamental circuit of a coloranalyzer of the present invention, wherein photovoltaic cells are used;

FIG. 11 is a characteristics diagram of the photovoltaic elements in thecolor analyzer of FIG. 10;

FIG. 12 is an embodiment of the circuit in FIG. 10;

FIG. 13 is a simplified circuit diagram of a unit detecting portion inthe embodiment shown in FIG. 6;

FIG. 14 is a circuit diagram showing a modification of the unitdetecting portion in FIG. 13, wherein transistors are used;

FIG. 15 is a circuit diagram of another embodiment of the analyzerincluding unit detecting portions of the construction shown in FIG. 14;

FIG. 16 is a graph showing the time variation characteristics ofluminance of light issuing from a limited portion of a fluorescentscreen of a color television tube;

FIG. 17 is a graph illustrating the output voltage characteristic of theunit detecting portion of FIG. 18 when a photometric system having thecircuit of FIG. 18 measures luminance of light issuing from a limitedportion of a fluorescent screen of a color television set;

FIG. 18 is a circuit diagram illustrating a modification of the circuitof FIG. 14, wherein a condenser is provided in parallel with a loadresistor so that the output of the circuit becomes what is illustratedin FIG. 17;

FIG. I9 is a circuit diagram of another embodiment formed by modifyingthe circuit of FIG. 15 and having the circuit of FIG. 18;

FIG. 20 is an exterior perspective view of the color analyzer, accordingto the present invention;

FIG. 21 is a perspective view showing the appearance of the memorydevice used in the color analyzer of FIG. 20; and

FIG. 22 is a perspective view of the light receiving portion of thecolor analyzer.

DETAILED DESCRIPTION It is known that a color constituted by an additivemixture of primary colors, such as the color of an image on thefluorescent screen of a color television, varies as the rate of energylevels or quantities of said primary colors. It is also known there isno variation in the spectral distribution of the relative radiant energyof each of the primary colors, and that there is only the increase anddecrease of said energy levels or quantities when said energy levels orquantities are increased and decreased to obtain a desired color. Forinstance, in the three primaries which constitute the colors issuingfrom the fluorescent screen of a color television tube, the spectraldistribution of the relative radiant energy of each of the primarycolors does not vary irrespective of any variation of the mixed colors.In other words, when the maximum value of the relative radiant energy isas sumed as l or I00, the distribution pattern of energy with respect tosaid maximum value does not vary, or has a normalized distributioncharacteristic irrespective of any variation of the mixed colors. Eachspectral energy distribution of the primary colors which constitute acertain particular color can be represented as a product of saidspectral distribution of the relative radiant energy (or a normalizedspectral energy distribution) and the coefficient (zero or certainpositive value) representing said energy level or quantity.

Assuming that a color to be measured consists of three primary colorshaving spectral distributions of the relative radiant energies B G andRA as shown in FIG. 1, and each coefficient of the energy levels of theprimary colors for the color to be measured is x x and x the spectralenergy distribution W, of the color is given by the following equationas a sum of each spectral energy distribution of the three primarycolors.

When a color having the spectral energy distribution W shown in equationI is detected by three detectors having spectral sensitivities S S and8,, respectively as shown in FIG. 3, the output C C and C of the detectors can be given by the following equations.

a=j r a x (2) CE] W. s. (3)

C I W S in practice, the spectral sensitivities and outputs of thedetectors can be obtained by an apparatus as shown in FIG. 5.

In the apparatus illustrated in FIG. 5, color input from the opticallens system is applied to three photoelectric elements P R and P eachhaving associated therewith a primary color filter F F or Frespectively. These filters and photoelectric elements cooperatingtherewith represent spectral sensitivities S,,, S and S in H0. 3, orS,,,, S and S in FIG. 4.

Furthermore, each photoelectric element P P P is connected to acorresponding indicating meter M M or M through an electric circuit.

By selection of the characteristics of the optical lens system 5,filters F F and F the photoelectric elements P P P,,, the indicatingmeters M M M and the electric circuits, the spectral sensitivity shownin FIG. 3 and FIG. 4 can be achieved with the apparatus of MG. 5.Consequently, the outputs C 3, C and C 2 read by the indicating meters MM and M respectively, in response to a color having the aforesaidspectral energy distribution characteristics W; satisfy the conditionsof equations 2 to 4.

Here, if the spectral sensitivity is set in such manner as iliustratedin FIG. 4, wherein the first curve S corresponds, for instance, to thespectral energy distribution R i the second curve Sy corresponds to thespectral energy (3;, and extends over the spectral band of the firstcurve S and the third curve S in which three primary colors areinvolved, the energy introduced into the detectors having spectra]sensitivities of S and S will become larger than that of S and S in FIG.3, so that amplified outputs can be obtained. This means that thedetectors having spectral sensitivities as shown in FIG. 4 are suitablefor the measurement of a color having weak energy.

Since the coefficients 1,, x and x; are represented by zero or apositive number for showing the energy levels or quantities of theprimary colors as set forth hereinbefore and are not dependent on thewave length i and since the spectral distributions of relative radiantenergy B G and R; and the spectral sensitivities S S and 8,, arefunctions of the wave length r as shown in FIGS. 1 and 3 by the curvesvarying in accordance with the wave length r the following equations canbe derived by substituting equation I in equations 2 to 4.

+ 72] A' G' k CR=XHI A'SR' A'i GJ A R' Jt data} A' R' A 10 zi=j r rr i22 A G' A er-I A' G' A .11 A' H' A A32=J GA'SR'QA Ry'sn'd 0 theequations 5 to 7 can be simplified as follows:

a ir :2 2. 13 1! Herein, the spectral sensitivities S S and 8,; arealways constant, and the spectral distribution of the relative radiantenergies of the primary colors do not vary insofar as said each spectraldistribution is that of the color issuing from the identical luminosity(which is, for instance, the fluorescent screen of a color television)as stated above. Therefore each integral term of equations 5, 6 and 7,that is A (i=l3,j=l3) in aqua tions 9, i0 and l I, can be considered asthe constant corresponding to said luminosity.

Thus, the output levels of the color analyzer C C C; can be given by thefollowing matrix expression:

Cg ii li t! ll 6 1: r: r: r;

n u sa I 45 By taking an inverse, the primary color output levels x xand 12,, from a color television cathode ray tube can be expressed inthe following manner:

By expanding the matrix equation l3, the following equations areobtained:

n ai' e+ s-:' c+ ss' n H in equations l4, l5 and 16, the coefficients D(i=I-3, j=l-3) represent individual terms of the in verse matrix of theaforesaid matrix of the equation l3 having coefficients A For instance,the coefficient 5 can be expressed in terms of A as follows:

ll It ll 3! n ll l! 3! n l:

In other words, D is a function of A (i=13,j=l3), and accordingly D is aconstant, because all of A are constants, as pointed out above.Similarly, it is easily seen that each of the coefficients D (i=13,j=l3)is constant.

Therefore, provided that the denominator of the right side of equation17 are known, the energy levels or quantities of the primary colors canbe obtained from the outputs of the detectors by solving matrix equation13, even if the spectral distributions of relative radiant energy ofeach of the primary colors overlap in part with each other and also thespectral distribution in each of the primary colors do not correspondwith the spectral sensitivity of the detector.

The principles related to the CIE chromaticity indication in the coloranalyzer according to the present invention, will next be described. Thespectral energy distribution W A as defined in equation 1, can berewritten as follows, according to the CIE method:

x=rwmtdl 18) Y=I AYA A z: m-m, 20

In equations 18 to 20 the term X, Y and Z represent tristimulus valuesof the CIE system with which any visible color can be specified in termsof the quantities of these stimuli and X, y and 2 represent spectraltristimulus values of the CIE system and satisfy the so-called LutherCondition.

The CIE chromaticity indication can be achieved as follows. Since, aspointed out above, the quantity of the primary colors x x and x areindependent of the wave length, the following equations can be easilyderived by substituting equation 1 in equations l8, l9 and 20:

In the equations 23 to 25, B G and R are spectral distributions of therelative radiant energy or normalized spectral energy distributions, andthe spec tral distributions of the spectral tristimulus values havefixed characteristics which have been determined by the CIE system, andintegrals of them are constant. Accordingly, each integral term in theequations 23 to 25 is constant, and such equations can be simplified asfollows:

By substituting equations 14, 15 and 16 in the equation 26, oneachieves:

II Is iz' zri m nn R (29) In the equation 29, the coefficients of theterm C C and C,, are constant and, hence, it can be simplified into thefollowing equation:

X I ii' n 12' r;+ ls' n 1 Similarly, equations 27 and 29 can berewritten as follows:

As described in the foregoing, the quantity of the primary colors of anarbitrary color from a television cathode ray tube can be detected byusing the output levels C C and C from a detector having differentspectral sensitivities for each primary color, as shown by equations 14,15 and 16. Furthermore, from the quantity of the primary colors x 1,,and 1: one can derive the quantities X, Y and Z of the CIE method, asshown by equations 26, 27 and 28. Of course, the quantities X, Y and Zcan be directly derived from the primary color output levels C C and Cas shown by equations 30, 31 and 32. With the quantities X, Y and Z thusdetermined, the CIE chromaticity can be calculated by the equations 2|and 22.

Thus, it will be understood that the quantities x x and it of theprimary colors can be obtained from the outputs C C and C of thedetectors by solving the equation 13 and the tristimulus values X, Y andZ of the CIE system can be independently obtained by solving theequations 26, 27 and 28. According to the invention, the matrixcalculation is carried out by an electric circuit to obtain thequantities of the primary colors from the output of said electriccircuit. In other words, in FIG. 2 showing the principle of theinvention, the light to be measured is introduced through the opticalsystem into the light receiving portion including a detecting means(Notedetecting means" is used for indicating the circuit of FIG. 14, thecircuits D D D in FIGS. 6, l5 and 19, the circuit of FIG. 18 having alight receiving member such as photoconductive cells or photovoltaiccells, so that said detecting means issue photometric output signals C CG and C R which correspond with each of the spectral sensitivitiesrespectively. Then, said signals are introduced into the electric matrixcircuit to carry out electrically therein a calculation of equation I3.The outputs of the electric matrix circuit are read by an indicatingmeter or the like.

FlG. 6 illustrates a fundamental circuit of the present invention, whichincludes cadmium sulfide (CdS) cells P P and P as light receivingmembers before each of which a color filter is respectively disposed asshown in FIG. 5. It will next be explained how the calculation ofequation 13 or equations l4, l5, 16 is carried out by the circuit of H6.6.

Upon the application of an arbitrary color, of which spectral energydistribution characteristics W, are given by equation l, each CdS cellproduces an output current C C or C depending on the spectralsensitivity S S or S in the direction as depicted by the arrow in thefigure. The outputs C C and C satisfy the conditions of equations 2, 3and 4. Each load resistor R, has a resistance value considerably smallerthan that of each CdS cell. The junctions between each pair of seriesconnected loading resistors R,, are grounded. As the output currentflows through the circuit com prising batteries E and E the CdS cell P Por P and the two load resistors R,, a positive voltage is produced atthe junction between the detector and one load resistor R,,, as shown bythe mark, while a negative voltage is produced at the junction betweenthe other load resistor R and the batteries, as shown by the mark. Themagnitude of the voltages thus produced is proportional to the intensityof the output from the CdS cell. If the resistance values of resistorsR, (i=l-9) are selected to be much larger than that of loading resistorR,,, the magnitude of the current through an indicating meter, forinstance meter M is given by the following equation:

s a/ 1) CB u/ 2) r; n a) CR Similarly, the magnitude of the currents llg through other indicating meters M M can be expressed as follows:

1C u/ 4) t; u/ s) CR u/ s) a In equations 33, 34 and 35, if thecoefficients of the output currents C C C, are denoted by G (t -F3,j=l-3), then those equations can be simplified as follows:

5 u' a i2' G ra ia 6) n ai a ilc ar ia In a comparison of equations 36,37, 38 with the preceding equations l4, l5, l6, if the conditions ofequation 8 so that A (i=1 3 ),j==l 3) are calculated; then 1),, ('Fl3,j=l 3) are determined by calculat ing equation l7; then the values ofD (i=1 3,j=l 3) obtained are inserted into the right side of equation 39in the left side of which are substituted the fractions ofR, and Ri (i=19) as shown in equations 33, 34. 35 to solve equation 39.

Such steps are, however, complicated and troublesome, and therefore theresistance values of resistors Ri (i=1 9) are obtained by conventionalmethods as de scribed hereinafter. It will be noted that the followingis a method for determining resistance values for the measurement of awhite chart pattern appearing on the fluorescent screen of a colortelevision tube. However, the method is also applicable for themeasurements of other similar patterns and the like for other similarapparatus.

For determining said resistance, firstly, the white chart pattern isgenerated on the fluorescent screen of the color television which isleft in its original condition (that is, the condition in which theinput to the television set is not adjusted), and then a standardpattern having a standard white color which has a color temperature inthe order of 96,500 or 9,300C. 27 MPCD is generated adjacent said whitechart pattern. For instance, a thin light reflecting plate is arrangedadjacent said chart pattern and is illuminated by a projec tor so as togenerate said standard white color thereon. Then, the two adjacentpatterns are compared with one another by the naked eye or by a suitabledevice to adjust the gain for each of the primary colors in the colortelevision to match the color of the chart pattern with that of thestandard pattern. After the matching operation, the device forgenerating the standard white color and including the thin plate and theprojector is removed.

Then, the light receiving part of the color analyzer is set opposite thechart pattern of the adjusted fluorescent screen, and then there isperformed an operation for generating one of the primary colors. Saidoperation is conducted by opening the circuits for generating the othertwo primary colors. Assuming that the firstly generated primary color isred, the color analyzer, which receives said red color only, is adjustedas to its values of the resistors R, and R (FIG. 6) so that the metersMG and M indicate zero on the scale. The green color is then generatedon the chart pattern, and the values of the resistors R and R areadjusted so that the meters M and M R indicate zero on the scale.Lastly, the blue color is generated on the chart pattern, and the valuesof the resistors R and R are adjusted so that the meters M and Mindicate zero on the scale.

Next, the entire circuits for the three primary colors are closed forgenerating the standard white color on the chart pattern, and values ofthe resistors R R and R are adjusted so that the meters M M and M Rincidate respectively one on the scale (unit) with respect to saidstandard white color.

Thus, the resistance values of the resistors Ri' (i=l 9) are onceadjusted, However, since the values of the resistors R,, R, and R arenot adjusted sufficiently in a prior operation, when the meter of one ofthe primary colors indicates zero on the scale, the meters for other twoprimary colors do not indicate zero on the scale (for instance, themeters M B and M do not indicate zero on the scale when the meter Mindicates zero).

Such unevenness is corrected by adjusting once more each of theresistors by generating each of the primary colors on the chart patternin the order of red, green, and blue so that the values of the resistorsR R and R are adjusted once more whereafter each meter indicates one onthe scale for the standard white color. Such correction can be repeatedtwo or three times.

Here, if the spectral sensitivity of the detectors is selected as whatis illustrated in FIG. 3, the deflection of the meter M shall beeffected mainly by the resistor R1, and the resistor Rw and Re serveonly for a minor adjustment. This means that the resistance of theresistor R1 is set sufficiently smaller than that of the resistors R2and R3. Similarly, the resistance of the resistors R4 and R7 are setsufficiently smaller than that of the other corresponding resistors.Thus the adjustment of the circuit is carried out primarily by the threeresistors R1, R4 and R7.

The manner for determining exact values for the resistors is describedin the above. When it is desired to know rough values for the resistorsfor judging an ad justing range thereof, a known circuit calculation canbe used by measuring the values C,,, C C of the out put current for thestandard white color, determining the values of the output currentrequired for oscillating the pointer of each of the meters over one unitof the scale (this can be done by utilizing a meter applicable in saidvalues of the output current), and setting the value of R, to the properone.

The color analyzer having the electric matrix circuit thus calibratedcan adjust, for each of the primary colors, the gain of a colortelevision set in a manner similar to that used in the calibration bygenerating the white chart pattern on the fluorescent screen, readingthe meters 12 12 and 12,, to determine aberrations of each of the valuesof the three primary colors which constitute said white color from thebasic value (which is, for instance, represented by one on the scale ofthe meter), and adjusting each of the values of the three primary colorsto agree with said basic value.

However, as can be seen from equation 8, the values of the term A(i=l3,j= l3) vary depending on the spectral distribution characteristicsof the fluorescent substances used for the primary colors in each colortelevision cathode ray tube. In other words, the values of the terms D(i=l-3, j==1-3) also change with the aforesaid variation of the cathoderay tube characteristics,as seen from equations l4, l and 16. In fact,after carrying out a number of tests on various kinds of colortelevision sets, it has been determined that there are considerabledifferences in primary color spectral characteristics among differentfluorescent substances. One calibration as mentioned above is sufficientfor one type of color television receiving set, but if it is desired tomeasure the primary color radiant energy levels of a plurality ofdifferent types of color television receiving sets, said calibrationshould be made each time the kind of fluorescent screen to be measuredis changed. According to tests which have been carried out forcalibration, it is necessary to prepare a particular color televisionset which is adapted to radiate reference or standard colors and, formeasurement of various kinds of color television sets, each televisionset requires a standard color radiating device having samecharacteristics as those of such television set.

In order to overcome such difficulties, another color analyzer accordingto the present invention, as shown in FIG. 7, uses calculating circuitsor the matrix circuits are made in the form of interchangeable blocks tobe detachably coupled to the main body of the analyzer, and a pluralityof matrix circuits are provided which are selected in accordance withthe subjects to be measured. Each of the aforesaid matrix circuits isprecalibrated in the manner set forth above to match with differentprimary color spectral energy distribution characteristics of thefluorescent substance of various color television cathode ray tubes, soas to satisfy the conditions of equations 14, 15 and 16 for each cathoderay tube. With such pre-calibrated matrix circuits, measurement ofcolors emanating from different color television cathode ray tubes canbe made simply by inter changing the matrix circuits for each cathoderay tube to be measured.

It should be noted that a plurality of such precalibrated matrixcircuits can be mounted on a color analyzer of the present invention, inconjunction with a selection switch which can be mounted on the mainbody thereof, so that the same effect as said interchanging of thepatchable matrix circuits can be achieved by turning the selectiveswitch to connect in a desired ma' trix circuit. In FIG. 6, such matrixcircuits are designated by being enclosed with dotted lines.

The memory device will next be described. As ex plained in theforegoing, without referring to any memory device, the color analyzer ofthe present invention can be calibrated by causing a color televisioncathode ray tube being measured to emanate one primary color light at atime and adjusting the calculating or matrix circuit of the analyzer toproduce only those output levels corresponding to said emanated primarycolor at the final stage indicating meters thereof. For instance,referring to equations 9, l0 and 11, if only a quantity of the primarycolor x is produced, the quantity of each primary colors can be given byBy substituting such relationship in equations 9, l0 and l l, the outputlevels from each detector or light receiving portion are given by ff llC(FAZI R si Similarly, when only one unit primary color output levelxi,- or x is radiated from the cathode ray tube being measured, thecorresponding output levels from he deleCtflrs be A12, A22, A32, 0r A13,A23, A33 respectively. In actual calibration, for instance in thecircuit of FIG. 6, as each unit primary color output emanates from thecathode ray tube being measured, electric currents equivalent to theaforesaid corresponding terms A,-,-(i 1- 3,1 I 3) flow through each CdScell circuit. Therefore, there are made preliminary arrangements ofmembers, with respect to which outputs may regularly be generatedcorresponding to said A,-,-(i=l 3, j=1 -3); that is, such members as areadapted for memorizing outputs of each of the light receiving membersthat are generated when said unit primary colors appear one by one onthe fluorescent screen of the color television. Such members shall eachhereinafter be referred as a memory member. Such memory member (whichcorresponds, for instance, with resistor groups in H0. 9) has no outputin and of itself, but output current flows therethough when the memberis connected to a certain power source. Thus, the same effects ofcorrection as in the case where the standard television is used can beachieved by substituting one after another the memory membersrespectively EOITBSPOIIClcamiration is, as mentioned above don e bygeneraii rig the standard white color of color television on thefluorescent screen.

As shown in equation 8, the values of the constants A (i=l-3, Fl-3)depend both on the spectral energy distribution characteristics of eachprimary color in the light from the fluorescent screeen of the colortelevision set to be measured and on the spectral sensitivitycharacteristics of the detectors and, accordingly, as the spectralenergy distribution of the phosphor varies, the values of said constantsalso vary. in other words, with a plurality of memory devices in thepresent invention, which are present for each unit primary coiorspectral energy distribution of phosphors of different color televisioncathode ray tubes, the color analyzer of the present invention can becalibrated, without having the particular cathode ray tube to bemeasured, simply by substituting the thusly present memory devices forthe light receiving members of the detecting means.

FIG. 9 shows one such memory device for CdS cells. Herein, theresistance values of various resistors are so selected that upon properactuation of the gangoperated change-over switches l3, l4 and 15,electric currents corresonding to the aforesaid constants A (i=l-3,j=l-3) flow through the respective circuits.

By providing a plurality of such memory devices mo unted on the coloranalyzer, together with a proper selector switch means (not shown) tomake proper selection of the memory devices for each cathode ray tube tobe measured, the operation of interchanging the memory device fordifferent cathode ray tubes can be dispensed with.

As pointed out in the foregoing, the memory device and the calculatingcircuit or matrix circuit correspond to the terms A (i=3, j=l3) asdefined in equation 8 and to the terms D (i=l3,j=l3) as defined inequations l4, l and 16. Thus, the principles of such memory device andthe calculating circuit can be used for the calculation of constantsrelated to the (HE chromaticity, such as C,,- (i=l-3, j=l-3) as definedin equations 26 and 28, as well as the terms E (i=l3,j=l3 as defined inequations 30, 31 and 32 (see FIGS. 10,12, and

Moreover, the unit quantity for the spectral energy distribution W of acolor from the light source to be measured, as shown in equation i, canbe seiected at any level at will, the values of the terms A,, (i=l3,j=l3), as defined in equation 8, depending on the unit color level. Thevalues of D (i=l3,j=l3) also vary depending on A (i=1-3, j=l-3), inother words, the aforesaid memory device and the calculating circuitmeans can respond to any A (i=l-3, j=l-3) and D (i=l-3, j=l3) and,accordingly, they can be used for storing and reproducing any color froma light to be measured. It is also possible to attach means for storingluminous energy to the aforesaid memory device, or to mount theaforesaid memory device directly on the main body of the color analyzer,for the sake of checking the calculating circuit. Similarly, checking ofthe light receiving portion, or detectors, can be facilitated bydirectly mounting both the aforesaid memory device and the calculatingcircuit on the main body of the color analyzer.

With reference to FIG. 13, showing the electric circuit related to adetector 9 of FIG. 6 while neglecting one of the loading resistors Rthere is the following relationship between the output voltage E,, theinternal resistance R, of the photoelectric detector (e.g., detector 9)the power source voltage E, and the load resis tance R,,:

As seen, the output voltage E is not exactly inversely proportional tothe internal resistance of the detector 9. Thus, even when the gradientcharacteristics of the photoelectric element, or the so-called y, is setat unity (l), the response of the output voltage to the incident lightenergy is not linear. This is a significant disadvam tage of the circuitarrangement of FIG. 13. in the detector circuit mentioned above withreference to H6. 6, the load resistance R, is selected to be negligibiysmall, compared with the internal resistance R, of the photoclectricelement, and only that portion in which the resistance of thephotoconductive cell is so high that the output of the detecting meansis approximately proportional to the incident light energy has beenused. Such usage of the photoelectric element is disadvantageous for thephotoelectric element.

On the other hand, in the embodiment shown in FIG. 14, if theresistances R and R, are so chosen as to make the base current i oftransistor T, negligibly small compared with current i through theresistance R then there is the following relation between the voltage Eacross the resistance R and the power source voltage E:

if the base-emitter voltage of the transistor T is designated as E andthe voltage across the photoelectric element P is represented as 5,,then the voltage E across the resistance R can be expressed as followsin terms of the two voltages:

E =E +E,

The base-emitter voltage of a transistor is in the order of about 0.3 Vfor germanium transistors and about 0.6 V for silicon transistors and,hence, if the voltage E, across the photoelectric element P is seiectedto be sufficiently large and in excess of 0.6 V, the equation 42 can besimplified as follows:

By substituting 41 for 43: n l lt t0 lt) 1' it is apparent from equation44 that the voltage E across the photoelectric element P is independentof the internal resistance R, thereof but depends on the

1. A color analyzer for determining individual primary color outputlevels of any light source constituted by the additive color mixture ofprimary color stimuli having an arbitrary but fixed spectraldistribution comprising: at least three photodetector means responsiveto different spectraL portions of the light emitted by said source andfor providing electric signals proportional to the light incidentthereon, the spectral sensitivity of each photodetector meanscorresponding with the spectral distribution of a given additive primarycolor; an electric matrix circuit means responsive to the signalsgenerated by the photodetector means for analyzing the information insaid signals by solving the following equation: xB A11 A12 A13 CB xG A21A22 A23 CG xR A31 A32 A33 CR wherein xb, xG and xR are the coefficientsof the energy levels of the blue, green and red additive primary colorstimuli respectively of the color to be measured, CB, CG and CR areintegral terms representing the color emitted by each additive primarycolor stimulus at a predetermined energy level represented by theaforementioned coefficients and as detected by each of saidphotodetector means with the aforementioned spectral sensitivities; andAij (i 1-3, j 1-3) are the integral terms corresponding to the coloremitted by each additive primary color stimulus regardless of the energylevel but due to its fixed energy level distribution which isindependent of energy level, and as detected by each of saidphotodetector means with the aforementioned spectral sensitivities; andindicator means connected to said matrix circuit means to indicate theenergy level of a respective one of the additive primary color stimuli.2. A color analyzer as claimed in claim 1 wherein: X E11 E12 E13 CB YE21 E22 E23 CG Z E31 E32 E33 CR wherein X, Y and Z are outputs of thematrix circuit means which correspond to C.I.E. tristimulus values ofthe color to be measured and Eij (i 1-3, j 1-3) where Cij.Dij (i 1-3, j1-3) where Cij are integral terms representing the color emitted by eachadditive primary color stimulus as detected by each detector means witha fixed C.I.E. tristumulus spectral distribution sensitivity, and whereDij represent individual terms of the inverse matrix of the aforesaidmatrix having coefficients Aij.
 3. A color analyzer as claimed in claim1 wherein each photodetector means includes a photoelectric cell and acolor filter for transmitting only light energy of a selected spectralband to the respective cell.
 4. A color analyzer as claimed in claim 1wherein said indicating means includes three indicators connectedrespectively with the outputs of the matrix circuit means.
 5. A coloranalyzer as claimed in claim 1 comprising a servo-system and wherein thematrix circuit means includes outputs connected with said servo-systemwhich adjusts automatically the quantity of each primary color.
 6. Acolor analyzer as claimed in claim 1 wherein each photodetector meanshas a spectral sensitivity corresponding respectively to each of thespectral energy distributions of the primary colors and the adjacentcharacteristic curves of the spectral sensitivities slightly overlapeach other.
 7. A color analyzer as claimed in claim 1 wherein the matrixcircuit means includes exchangeable circuits independent of one anotherand having different circuit constants.
 8. A color analyzer as claimedin claim 7 wherein more than two matrix circuits are provided selectablycorresponding to the characteristics of an object to be measured.
 9. Acolor analyzer as claimed in claim 1 including memory members andwherein the photodetector means are exchangeable with the memory membersto obtain electric signals corresponding to outputs of the photodetectormeans which receive a light of standard color.
 10. A color analyzer asclAimed in claim 9 further comprising more than one group of memorymembers which are exchangeable for the photodetector means.
 11. A coloranalyzer as claimed in claim 1 wherein each photodetector meanscomprises a photoconductive cell, load resistances, and a transistorincluding an emitter connected with the photoconductive cell and acollector connected with the load resistances in series.
 12. A coloranalyzer as claimed in claim 11 wherein each photodetector meansincludes two condensers connected respectively in parallel with one ofthe load resistances.
 13. A color analyzer as claimed in claim 12further comprising a plurality of condensers connected respectively inparallel with each load resistance.
 14. A color analyzer as claimed inclaim 1 wherein each photodetector means comprises a photovoltaic cell,a differential amplifier circuit, one terminal of the cell beingconnected with one input terminal of the amplifier circuit, and afeed-back resistance, the output terminal of the amplifier circuit beingconnected with said terminal fo the cell through the feedbackresistance.
 15. A color analyzer as claimed in claim 14 wherein theelectric matrix circuit includes said feedback resistances and sixfurther resistances.
 16. A color analyzer as claimed in claim 15 whereineach amplifier circuit includes two field effect transistors.
 17. Acolor analyzer as claimed in claim 16 further comprising threecondensers connected respectively in parallel with said feedbackresistance.